Impact of body composition on fragility fractures in US elderly adults: a population-based study.

Objectives: The aim of this study was to investigate how variations in body composition impact the likelihood and location of fragility fractures in older adults.

Methods: Data of US adults aged ≥ 60 years with fragility fracture and body dimension records (n = 13177, representing approximately 334 million US elderly adults) were from NHANES between 1999 and March 2020. We calculated body composition parameters, including the body roundness index (BRI), weight-adjusted waist index (WWI), abdominal visceral fat index (AVI), and arm-to-waist circumference ratio (AC/WC). Linear regression analyzed trends in site-specific fragility fractures, while logistic regression assessed the separate and joint effects of parameters.

Results: Fragility fractures increased, especially among elderly with central obesity. A rounded body shape (OR_{4.42 ≤ BRI ≤ 5.60} = 0.6, 95% CI, 0.4-0.9; OR_{5.61 ≤ BRI ≤ 7.00} = 0.5, 95% CI, 0.3-0.8; OR_{BRI ≥7.01} = 0.4, 95% CI, 0.2-0.8) and a balanced arm-to-waist size (OR_{0.32 ≤ AC/WC ≤ 0.33} = 0.6, 95% CI, 0.4-0.9) reduced the risk of hip fractures, and a moderate fat content (OR_{11.45 cm/√kg ≤WWI≤1.93 cm/√kg} = 0.6; 95% CI, 0.4-1.0) lowered the risk of vertebral fractures. Joint analyses found that moderate-built (OR_{BRI < 4.42, 10.96 cm/√kg ≤WWI≤11.44 cm/√kg} = 1.9, 95% CI, 1.3-3.0) elderly faced doubled risk of hip fractures compared to those with severe central obesity (BRI ≥ 7.01, WWI 11.45-11.93 cm/√kg), while mild obesity (OR_{5.61≤ BRI≤7.00, WWI < 10.96 cm/√kg} = 0.1, 95% CI, 0.0-0.6) carried only 10% of this risk. A stocky physique (OR_{BRI ≥ 7.01, AVI 20.48-23.44 cm²/1000} = 3.6, 95% CI, 1.1-11.1) was a significant risk factor for vertebral fragility fractures, while fit individuals with strong arms (OR_{BRI < 4.42, AC/WC ≥ 0.34} = 0.7, 95% CI, 0.5-1.0) experienced a lower incidence of vertebral fractures.

Conclusions: This population-based cohort study identified distinct risk groups for fragility fractures and clearly visualized these high-risk populations, which contributes to preventing fragility fractures and reduce the risk of second fractures.